/*
 * Copyright 2007-2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License. 
 * 
 * Project: JGentleFramework
 */
package org.aopalliance.intercept;

/**
 * Intercepts the construction of a new object.
 * <p>
 * The user should implement the {@link #construct(ConstructorInvocation)}
 * method to modify the original behavior. E.g. the following class implements a
 * singleton interceptor (allows only one unique instance for the intercepted
 * class):
 * 
 * <pre class=code>
 * class DebuggingInterceptor implements ConstructorInterceptor {
 * 	Object	instance	= null;
 * 
 * 	Object construct(ConstructorInvocation i) throws Throwable {
 * 
 * 		if (instance == null) {
 * 			return instance = i.proceed();
 * 		}
 * 		else {
 * 			throw new Exception(&quot;singleton does not allow multiple instance&quot;);
 * 		}
 * 	}
 * }
 * </pre>
 */
public interface ConstructorInterceptor extends Interceptor {
	/**
	 * Implement this method to perform extra treatments before and after the
	 * consrution of a new object. Polite implementations would certainly like
	 * to invoke {@link Joinpoint#proceed()}.
	 * 
	 * @param invocation
	 *            the construction joinpoint
	 * @return the newly created object, which is also the result of the call to
	 *         {@link Joinpoint#proceed()}, might be replaced by the
	 *         interceptor.
	 * @throws Throwable
	 *             if the interceptors or the target-object throws an exception.
	 */
	Object construct(ConstructorInvocation invocation) throws Throwable;
}
